[Libraries][iOS] Microsoft.Extensions.FileProviders.Physical PhysicalFileProviderTests failure

[mdh1418]

Discovered in unrelated PR for iOSSimulator x64 Release #57208

Microsoft.Extensions.FileProviders.PhysicalFileProviderTests.TokenForEmptyFilter
    Assert.False() Failure\nExpected: False\nActual:   True

Build: https://dev.azure.com/dnceng/public/_build/results?buildId=1337772&view=logs&j=accacb66-0a14-52ef-4079-6344686d9d4c&t=34fbd35e-866b-51a1-9063-fb50703b1957
Log: https://helixre8s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-57208-merge-9e0e0de14f9742ad80/Microsoft.Extensions.FileProviders.Physical.Tests/1/console.c669c194.log?sv=2019-07-07&se=2021-09-22T16%3A10%3A24Z&sr=c&sp=rl&sig=wEpzOzHKwO8SjGbfSRJ9Ionr6BXHZl%2F%2FcV85ey68eyA%3D

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Issue Details

---

Discovered in unrelated PR for iOSSimulator x64 Release #57208

Microsoft.Extensions.FileProviders.PhysicalFileProviderTests.TokenForEmptyFilter
    Assert.False() Failure\nExpected: False\nActual:   True

Build: https://dev.azure.com/dnceng/public/_build/results?buildId=1337772&view=logs&j=accacb66-0a14-52ef-4079-6344686d9d4c&t=34fbd35e-866b-51a1-9063-fb50703b1957
Log: https://helixre8s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-57208-merge-9e0e0de14f9742ad80/Microsoft.Extensions.FileProviders.Physical.Tests/1/console.c669c194.log?sv=2019-07-07&se=2021-09-22T16%3A10%3A24Z&sr=c&sp=rl&sig=wEpzOzHKwO8SjGbfSRJ9Ionr6BXHZl%2F%2FcV85ey68eyA%3D

Author:	mdh1418
Assignees:	-
Labels:	untriaged, area-Extensions-FileSystem
Milestone:	-

[danmoseley]

Let's include full stacks.

        <failure exception-type="Xunit.Sdk.FalseException">
          <message><![CDATA[Assert.False() Failure\nExpected: False\nActual:   True]]></message>
          <stack-trace><![CDATA[   at Microsoft.Extensions.FileProviders.PhysicalFileProviderTests.TokenForEmptyFilter()
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)]]></stack-trace>
        </failure>

@mdh1418 is it surprising there's no line number? Is the pdb not getting deployed on iOSSimulator? It makes diagnosis harder.

[danmoseley]

                using (var provider = new PhysicalFileProvider(root.RootPath))
                {
                    var token = provider.Watch(string.Empty);

                    Assert.False(token.HasChanged);  // <<<<<
                    Assert.True(token.ActiveChangeCallbacks); 
                }

I think this means that the last write time of the root directory of the DisposableFileSystem changed. But that is unique to this test
RootPath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

Some kind of OS delay ?

[mdh1418]

Edit: Mistakenly commented on wrong issue!

[mdh1418]

As of commit 349d811, the test passes on iOSSimulator x64 Debug locally.